From 748b1681549067f2e27ab2b9102ef9352cfa8a4c Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Mon, 7 Oct 2024 01:20:43 +0200
Subject: [PATCH] libbb: move is_in_supplementary_groups() from test to libbb

function                                             old     new   delta
is_in_supplementary_groups                             -      54     +54
nexpr                                                766     721     -45
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 54/-45)              Total: 9 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
 coreutils/test.c     | 20 +-------------------
 include/libbb.h      |  5 +++++
 libbb/bb_getgroups.c | 20 ++++++++++++++++++++
 3 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/coreutils/test.c b/coreutils/test.c
index c02c92745..874285704 100644
--- a/coreutils/test.c
+++ b/coreutils/test.c
@@ -637,32 +637,14 @@ static int binop(void)
 	/*return 1; - NOTREACHED */
 }
 
-static void initialize_group_array(void)
-{
-	group_array = bb_getgroups(&ngroups, NULL);
-}
-
 /* Return non-zero if GID is one that we have in our groups list. */
-//XXX: FIXME: duplicate of existing libbb function?
-// see toplevel TODO file:
-// possible code duplication ingroup() and is_a_group_member()
 static int is_a_group_member(gid_t gid)
 {
-	int i;
-
 	/* Short-circuit if possible, maybe saving a call to getgroups(). */
 	if (gid == getgid() || gid == getegid())
 		return 1;
 
-	if (ngroups == 0)
-		initialize_group_array();
-
-	/* Search through the list looking for GID. */
-	for (i = 0; i < ngroups; i++)
-		if (gid == group_array[i])
-			return 1;
-
-	return 0;
+	return is_in_supplementary_groups(&ngroups, &group_array, gid);
 }
 
 /*
diff --git a/include/libbb.h b/include/libbb.h
index 67e7bf7b9..e06aef08e 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1201,6 +1201,11 @@ void die_if_bad_username(const char* name) FAST_FUNC;
  * Dies on errors (on Linux, only xrealloc can cause this, not internal getgroups call).
  */
 gid_t *bb_getgroups(int *ngroups, gid_t *group_array) FAST_FUNC;
+/*
+ * True if GID is in our getgroups() result.
+ * getgroups() is cached in group_array[], to makse successive calls faster.
+ */
+int FAST_FUNC is_in_supplementary_groups(int *pngroups, gid_t **pgroup_array, gid_t gid);
 
 #if ENABLE_FEATURE_UTMP
 void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname);
diff --git a/libbb/bb_getgroups.c b/libbb/bb_getgroups.c
index 5d83c729a..f030d5eac 100644
--- a/libbb/bb_getgroups.c
+++ b/libbb/bb_getgroups.c
@@ -45,3 +45,23 @@ gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
 		*ngroups = n;
 	return group_array;
 }
+
+/* Return non-zero if GID is in our supplementary group list. */
+int FAST_FUNC is_in_supplementary_groups(int *pngroups, gid_t **pgroup_array, gid_t gid)
+{
+	int i;
+	int ngroups;
+	gid_t *group_array;
+
+	if (*pngroups == 0)
+		*pgroup_array = bb_getgroups(pngroups, NULL);
+	ngroups = *pngroups;
+	group_array = *pgroup_array;
+
+	/* Search through the list looking for GID. */
+	for (i = 0; i < ngroups; i++)
+		if (gid == group_array[i])
+			return 1;
+
+	return 0;
+}